Pentair Pentek R Series Cartridges are manufactured from a durable, non-woven and reusable polyester fabric that is suitable for a wide range of filtration uses. The media is pleated around a polypropylene core for added strength. The pleated endcaps of the standard cartridges are immersed in a thermo-setting vinyl plastisol. The Big Blue cartridges have a molded endcap with gaskets. The pleated ends are sealed to the endcap with a thermoplastic adhesive. The overlap seam is sonically welded to reduce internal bypass improving filtration efficiency. The standard 9.75" length cartridge has more than four square feet of polyester fabric, while the larger Big Blue version has more than 16 square feet. The media is pleated to maximize dirt holding capacity and extend the time period between changes or cleaning.